Re: [HACKERS] path toward faster partition pruning

Hello Amit,

Thanks for the updated patches

On Wed, Oct 25, 2017 at 1:07 PM, Amit Langote
<Langote_Amit_f8@lab.ntt.co.jp> wrote:
> On 2017/10/25 15:47, Amit Langote wrote:
>> On 2017/10/24 1:38, Beena Emerson wrote:
>>> I had noticed this and also that this crash:
>>>
>>> tprt PARTITION BY RANGE(Col1)
>>>        tprt_1 FOR VALUES FROM (1) TO (50001) PARTITION BY RANGE(Col1)
>>>               tprt_11 FOR VALUES FROM (1) TO (10000),
>>>               tprt_1d DEFAULT
>>>        tprt_2 FOR VALUES FROM (50001) TO (100001)
>>>
>>> EXPLAIN (COSTS OFF) SELECT * FROM tprt WHERE col1 BETWEEN 20000 AND 70000;
>>> server closed the connection unexpectedly
>>> This probably means the server terminated abnormally
>>> before or while processing the request.
>>> The connection to the server was lost. Attempting reset: Failed.
>>> !>
>>
>> ...and this (crash) were due to bugs in the 0005 patch.
>
> [ .... ]
>
>> Should be fixed in the attached updated version.
>
> Oops, not quite.  The crash that Beena reported wasn't fixed (or rather
> reintroduced by some unrelated change after once confirming it was fixed).
>
> Really fixed this time.
>

The crashes are fixed. However, handling of DEFAULT partition in
various queries is not proper.

Case 1: In this case default should be selected.DROP TABLE tprt; CREATE TABLE tprt (col1 int, col2 int) PARTITION BY
range(col1);CREATE TABLE tprt_1 PARTITION OF tprt FOR VALUES FROM (1) TO (50001)
 
PARTITION BY list(col1); CREATE TABLE tprt_11 PARTITION OF tprt_1 FOR VALUES IN (20000, 25000); CREATE TABLE tprt_12
PARTITIONOF tprt_1 FOR VALUES IN (50000, 35000); CREATE TABLE tprt_13 PARTITION OF tprt_1 FOR VALUES IN (10000); CREATE
TABLEtprt_1d PARTITION OF tprt_1 DEFAULT;
 


postgres=#  EXPLAIN (COSTS OFF) SELECT * FROM tprt WHERE col1 < 10000;       QUERY PLAN
--------------------------Result  One-Time Filter: false
(2 rows)


Case 2: In this case DEFAULT need not be selected.

DROP TABLE  tprt; CREATE TABLE tprt (col1 int, col2 int) PARTITION BY range(col1); CREATE TABLE tprt_1 PARTITION OF
tprtFOR VALUES FROM (1) TO (50001)
 
PARTITION BY range(col1); CREATE TABLE tprt_11 PARTITION OF tprt_1 FOR VALUES FROM (1) TO (10000); CREATE TABLE tprt_12
PARTITIONOF tprt_1 FOR VALUES FROM (10000) TO (20000); CREATE TABLE tprt_13 PARTITION OF tprt_1 FOR VALUES FROM (20000)
TO(30000); CREATE TABLE tprt_1d PARTITION OF tprt_1 DEFAULT; INSERT INTO tprt SELECT generate_series(1,50000),
generate_series(1,50000);

postgres=#  EXPLAIN (COSTS OFF) SELECT * FROM tprt WHERE col1 < 10000;          QUERY PLAN
--------------------------------Append  ->  Seq Scan on tprt_11        Filter: (col1 < 10000)  ->  Seq Scan on tprt_1d
     Filter: (col1 < 10000)
 
(5 rows)


-- 

Beena Emerson

EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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